Clay and method of mixing it with water



CLAY AND METHOD OF q WITH WATER Paul Bechtnef and Winfred B. Hirschmann,Chicago, Ill., asslgnors, by mesne assignments, to American Colloid 00.,Chicago, Ill., a corporation of South Dakota No Drawing. ApplicationDecember 7, 1936, Serial No. 114,712

4 Claims.

The present invention relates to improvements of clays and methods ofmixing them with water. It has for an object the making of smoothermixtures of clay in water by simple and more rapid methods thanpreviously employed.

Another object is to incorporate the clays readily with water withouthindering the desirable gelatinizing and swelling properties.

A third object is to prepare the mixtures substantially free from clotsor lumps of unsaturated solids.

Another object is to form dispersions, slurries,

or gels of higher concentrations than are possible by the presentmethods.

An additional object. is to make such mixtures of clay and water bycontinuous as distinguished from batch processes.

A still further object is to provide a clay which is adapted for use inthis continuous mixing process.

A further object is to permit utilization of the finely dividedfractions of a pulverized clay in forming suspensions.

The present invention represents an improvement over the clay and theprocesses disclosed in our U. S. Patent No. 2,036,617. In this patent, aprocess was disclosed whereby diflicultly slakable clays such asbentonitic clay, could be rendered readily slakable by limiting theparticle size between an upper and a lower limit. This had the effect ofremoving the large particles into which water penetrated very slowly andalso removed the fines or powdered fractions which tended to float orform into agglomerates which resisited wetting.

We have further discovered that by suitable handling of the pulverizedclays we can disperse them just as readily as the selectively sized onesand we have also discovered that there are certain degrees ofpulverization which are more easily mixable by such handling thanothers. Of course it will be understood that a clay which has to becarefully sized to both an upper and a lower limit is more expensiveboth as to grinding and as to screening than a clay which can be merelyground and perhaps screened once.

Our invention embraces specifically clays that are difiicult to slake ordisperse, or mix smoothly in water. Such clays are extensively used inindustrial processes in the form of a soft mud, paste, or slip, as inceramic processes, in the mud-ladenfluid method of drilling oil and gaswells, in the paper industry, in some phases of foundry work, in makingemulsions of asphalt or other water immiscibles, in horticulturalsprays, and in the manufacture of soaps and polishes.

glii their common commercial forms such clays are difiicult to mixsmoothly with water to form the paste or dispersion that is required forthese 5 uses. When added to water in lump form, they sink immediately tothe bottom of the vessel and resist soaking to a surprising degree. Evenafter hours or days of standing the lumps frequently have hard and drycenters. On the other hand, 10 when a mass of such clays in a finelypowdered form is added to water in a vessel, it will float on the watersurface; the particles immediately in contact with the water swellrapidly to close the voids and passages to the interior of the mass, 35resulting in agglomerates with a sticky water sealing coating and a softbut dry interior. Attempts to stir masses of such powdered clays resultin the formation of clots or unsaturated agglomerates which adheretenaciously to the 20 paddles of the mixing equipment. While these caneventually be broken up, much time and power is required to do so. Inaddition, the stiffness of the muds formed with these clays is so great,that it is practically impossible to make concentrations greater than 15to 17% with the usual type of stirring or agitating apparatus.

There are known methods by which such diificultly slakable clays may beincorporated with water fairly readily, but such methods haveobjectionable features. One of these means, for example, is to useelectrolytes either mixed with the clay or dissolved in the water. Theyare effective but have the disadvantage of altering the properties ofthe clay to the detriment of its employment for some purposes. Anothermethod is to pre-heat the clay to temperatures at which some of itschemically-combined water is driven off, but in doing so, some of itsuseful properties are inhibited in proportion to the degree of heatwhich has been applied. Another method is to make a paste of thepulverized clay with alcohol, acetone or other water soluble fluid andthen mix with water. This is obviously expensive. A further means is toblend the dried clay with some inert material such as whiting orpowdered silica, etc., which help keep the particles from agglomeratingand permit the water to enter them more readily. This however, changesthe character of the product. Furthermore, most of these methm ods havethe disadvantage of being batch instead of continuous processes.

In carrying out this invention we prepare masses or aggregates of groundclays in such form that they can be readily wetted, and then contactsuch masses or aggregates with water in a special manner. To illustrate,by suitable means we spread out a stream of water into a thin sheet andhave a similar sheet of clay fiow onto it. The thickness of the claysheet is such that the water can penetrate through it before theparticles on the surface touching the water can swell to form agelatinous layer which would seal off further penetration. This is animprovement which extends the principle of our patent above referred towhich discloses the dispersion of the selectively sized grains, whichare prepared not only so that they are self-immersible but also of suchdiameter thatthe water can penetrate to their cores before the surfaceparticles swell to form a gelatinous sealing layer. In this case of thepulverized materials in sheet form, it is not an individual particlethat is prepared of such diameter, but a group of finer particles whichare aggregated in layers of such thickness. It follows, therefore, thatthe individual particles in the layer must not exceed the upper sizelimit of the critical slaking range for the particular clay.

As a concrete illustration of a method of carrying out this novelinvention, we give the following description:

Water is spread out into the form of a sheet by forcing it underpressure through a slot or other common means, and clay is sprinkledonto that sheet in thin layered form. That is, water coming from a pipemay be spread out in the form of a ribbon instead of flowing out in theshape of a cylinder as is customary. The clay may also be spread out inthe form of a ribbon. Incorporation of these two fiat streams will makea simple mixture readily. The water may be continuously fresh withoutany clay mixed in with it, or it may be re-circulated from a tank sothat the concentration is gradually built up or it may be a natural orartificial watery fiuid containing finely divided solids or othersubstantially non-ionizing materials.

The ground clay maybe put in ribbon form in several ways. One employs avibrating feeder. This apparatus consists of a hopper with a troughunderneath it that is vibrated by means of an electro-magneticoscillator. It is well known that pulverized clays, such as the commoncommercial form of about 90% through a 200 mesh sieve, do not flow outof hoppers uniformly and spontaneously. Some external assistance isusually required; the vibrator is one means of supplying it. It causesthe material to flow from the hopper over the trough, and by adjustingthe amplitude of vibration, the rate of flow of the clay can beregulated. With the trough in the shape of a broad fan, the clay comingfrom the bottom of the hopper can be spread out into a thin layer. If itfalls onto a broad, thin, fanshaped stream of water directly beneath, itwill soak up at once to make a dispersion. The trough can be fiat,convex, or take any of numerous obvious forms, with the water streampreferably having the same general shape and dimensions. Furthermore,instead of having the clay fed from the hopper over a trough, we canhave it fall out of a hole in the bottom of a funnel shaped hopper ontothe apex of a vertical cone centered beneath the hole to which avibrator is also attached. By the time the clay reaches thecircumference of the base of the cone it is spread out in a very thinlayer so that when it falls onto a surrounded or enclosed cone-shaped toform a practically lumpless slurry.

. Per cent -40+50 mesh 9 -50+60 do 19 ,;e60+80 do 13 -80+100 d '10-100+140 do 16 -140+200 do 13 -200 do 20 It is to be noted that thisanaylsis shows quite a proportion of particles to be finer than 200mesh. Such fine grains do not hinder the uniformity of flow through thenarrow openings unless the. amount of them present is too large. Insuch'cases it is necessary to remove them entirely or to remove enoughof them to get a mass of particles that flows freely. This eliminationof dust will result in grades of size ranges such as for example 50 mesh+200 mesh or -100 mesh +200 mesh. There is really no limit to thefineness of the particles that can be present. Their proportion is whatcounts and so long as the clay flows freely through narrow slots to formsmooth water mixtures, it is satisfactory for the purpose of thisinvention.

The maximum size of particles as well as the thickness of the claymasses or layers is limited by the rate of swelling of the clay. Thoseclays which form impervious surface layers fast are restricted torelatively small particles and layer thicknesses, while those whichswell more slowly can have larger ones present. In general, we havefound that clay masses consisting largely of particles greater than 0.02inch wet too slowly to be useful, and are consequently beyond the scopeof this invention.

By the use of such readily flowing materials we can make mixtures ofwater and diflicultly slakable clays quickly, easily, and with verysimple equipment, and consequently the size ranges of easily dispersiblematerials covered in our U. S. Patent No. 2,036,617 are extended. Suchspontaneously flowing materials also facilitate greatly in making upother mixtures such as dry blends.

We have found that a spray gun is another means of preparing the clay ineasily wetted form and making water mixtures. A stream of dust can beblown against an atomized jet of moisture coming out of a spray nozzleto form a suspension or paste, depending on the relative proportions ofthe materials. The method is subject to considerable flexibility, andrequires as a whole but one precaution: the angle at which the streamsintersect should be quite small. If they meet each other at rightangles, the force and speed of the air carries some of the powderthrough the spray without being wetted. If, however, the two jets areaimed in the same direction so that they flow almost parallel to eachother, they blend and much more complete mixing results.

One method of using the spray gun type of apparatus consists in havingboth jets in the form of thin, broad fans. When these are paralleled andbrought together with a small angle between them, much more thoroughmixing results because it is spread over a much larger space.

Instead of a thick stream of solids meeting a thick stream of liquids,individual particles of dust meet individual droplets of fluid.Naturally there is much less chance for particles to escape beingwettedi and much less chance for agglomerates to form. With a fan-shapedjet of slide at will.

dust enclosed between two fan-shaped Jets of liquid, the blending isstill better.

There are many variations of the above use of a spray apparatus forbringing the clay and water together. For example, they can be blown outof concentric openings with the powder on the inside sojthat it isimprisoned and cannot escape being wetted, particularly if the two jetsare almost parallel. Also, the jets can be given twisting or twirlingmotions or be varied from circular or very wide, broad fans topractically any other form desired. In addition, the air for blowing theclay into contact with the water can be replaced bysteam which willnaturally condense on contact with the water and therefore prevent theoccurrence of disturbing currents of air which tend to carry out of thereceiving vessel some of the spray of the paste or suspension formed. Itmay also be desired to have the water in the vapor state to formproducts which are only slightly wetted.

To illustrate the ease with which dispersions of dimcultly slakableclays can be formed with our invention, we cite the following examples:

Example 1.Pulverized gel-forming bentonite was caused to fiov' over arectangular trough of a vibrating feeder. It dropped ofi the end of thetrough in a thin layer onto a sheet of water. In 2 minutes, 100 poundsof a smooth mixture was formed.

Example 2. A mixture of the same clay was also made with water by meansof a modification of the ordinary paint spraying apparatus. The

powdered clay was put into a container and by means of a jet of air,blown out of an opening directed at a fine spray of water. A uniform mudor concentration resulted at once.

Example 3.A typical gel-forming clay from the Black Hills region wasground to the following sieve analysis:

Percent mesh 50+ do 19 60+ do 13 80-1-100 do 10 +140 do 16 -+200 do; 13-200 do 20 It was then put into a container with a slot in the bottomwhose dimensions were 1% by 36", and which could be opened or closed bya The hopper bottom shape permitted all the clay to run out. Drectlyunderneath the slot, and paralleling the direction of flow of the claywas fastened a device out of which water would flow in a sheet also 36"wide. The water was turned on and its flow adjusted to the rate ofpounds per minute and the slide opened so that the clay would flow outat the rate of 40 pounds per minute. In 20 minutes 4000 pounds of asmooth mud of 20% concentration was formed.

Example 4.-For comparison with the above rapid and economical method, aslightly smaller quantity of the same bentonite pulverized so that 90%passes through a 200 mesh sieve, was made into a paste by means ofordinary mixing machinery using a tank type mixer having a heavyagitator with alternating blades revolving in op- ;posite directions.The water was put into the tank first and the clay added at the bestrate to permit the machinery to operate smoothly under the direction ofa man experienced in clay mixing. The results indicated a requirement of5 horsepower and 2 hours of mixing to produce 4,000 pounds of a pastecontaining 17% of the clay.

All these means are applications of our fundamental invention ofseparating the particles, of ground clay into masses or aggregates ofsuch thickness that they can be readily wetted, and contacting them withwater. They not only permil: the same materials and the same quantitiesof them to be brought together as is possible in present processes, butalso allow a wider range of proportions to be employed. They have thedesirable features of being continuous and simple. Furthermore, if theproduct is to be used as a coating compound, it can be sprayed on thesurface to be covered without the necessity of collecting it in acontainer and then applying it with a brush. The materials can thereforebe incorporated and/or used with the saving of time and expense.

With regard to all of the above methods of mixing the pulverized claywith water it is to be noted that in case a layer is formed this layermust be of such thickness that water can penetrate the layer thoroughlybefore the surface particles swell and seal the layer against furtherpenetration of water. If aggregates of fine particles are formed such asby air spraying, the thickness of the aggregates must likewise be suchthat the water can completely wet the aggregates before the surfaceparticles swell and close off further water. In the case of the airspray the particles may be regulated by varying the relation betweenclay and air used. The proper adjustment is obtained when the mixture ordispersion is substantially free from clots or lumps of unsaturatedparticles. In the case of the flowing layers the flow of clay and theaction of the vibrator or other factors employed will be adjusted tohave the layer delivered to the water at this required thickness.

As has been pointed out, this invention also contemplates a clay of suchparticle size that it can be employed in continuously forming thesedispersions or mixtures without the use of flow hastening means.Therefore, the clay is prepared so as to flow spontaneously from anopening of such size as to give the desired layer thick ness. For thisreason the particles are kept below the upper limit described and willalso be freed from an excessive quantity of fines which have the effectof preventing spontaneous flowing.

While the specification has referred sp :cifically to making mixtures ofclays with water, it is evident that this water does not necessarilyhave to be pure or free from other substances. It may contain inertsolids such as sand, barytes, iron oxide, etc., as occur in drillingmuds or other manufactured fluids, or it may be a natural mixture suchas rubber latex. The applicability of these water mixtures or solutionsto this invention is restricted only by the ions or other materials thatthey contain, which should not be of such character or concentration asto hinder significantly the swelling or self-suspendability orgelatinizability or other colloidal properties of the clay. The termwater" as used in the specifications and claims, therefore refers not 15culy to the pure liquid but also to such mixtures and/or solutions.

The invention is also adapted to making mixtures of clays with drymaterials such as sands or powders or other compositions. Besides thecontinuous and automatic qualities, these materials and methods promotequick and uniform blending because of being spread out into thin layers.I

It is obvious that various changes and modi flcations may be made in thedetails of construction and design of the above specifically describedembodiment of this invention without departing from the spirit thereof,such changesand modifications being restricted only by the scope of thefollowing claims.

What is claimed is:

1. A-mass of particles of bentonitic clay prepared so that they are allless than the critical slaking size with only enough of the finestparti- 'cles removed to permit the mass to flow spontaneously through aslot 6" wide whereby when allowed to run out of such slot onto a runningsheet of water it will mix therewith to produce a mud or slip.

2. The continuous method of dispersing a diillcultly slakable clay belowthe critical slaking size range in water which comprises producing arunning stream of clay with its particles less than 0.02" in diameterand of a size to flow spontaneously out of a slot wide, spreading theclay into a thin layer of such thickness that water can penetrate andthoroughly wet the clay stream before its surface swells and seals oithe water, producing a similar thin layer of water, and bringing thestream of clay into contact with the stream of water with both streamsflowing in substantially the same gen-' eral direction. I I

3. The process of preparing dispersions, emulsions, gels, pastes orslips continuously from bentonitic clay which comprises preparing theclay so that its particles are less than 0.02" in diameter and of a sizeto flow spontaneously out of a slot 1 wide, spreading the clay into athin layer and contacting the layer of clay with a similar layer ofwater flowing in the same eral direction as the layer of clay.

4. The method of preparing mixtures of hentonitic clay and water whichconsists in spreading clay of particles below the upper limit of thecritical slaking size range into a layer of a thickness such that watercan penetrate therethrough before the outer surface of the layer swellsto exclude further water, and bringing the layer of clay into contactwith a similar layer of water.

PAUL BECHTNER. WINFRED B. HIRSCHLMNN.

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